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Modeling >> Behavioral Models >> Plot I-V Curve by Using Matlab
https://designers-guide.org/forum/YaBB.pl?num=1163994060

Message started by qiushidaren on Nov 19^th, 2006, 7:40pm

Title: Plot I-V Curve by Using Matlab
Post by qiushidaren on Nov 19^th, 2006, 7:40pm

Hi all, I want to plot an i-v curve of this equation i=100*[1.3-v+500*(5-i)]^2 by using Matlab, but unfortunately it looks that the plot I get isn’t the one that I want, so I think there must be something wrong but I don’t know it. Your suggestions and comments will be highly appreciated!
Here is my code:

Quote:

%current versus voltage curve
v=0:0.1:3;
i=100*[1.3-v+500*(5-i)].^2;
plot(v,i)
title('current versus voltage of 2.6(c)')
xlabel('Voltage(V)')
ylabel('Current(uA)')
grid

Title: Re: Plot I-V Curve by Using Matlab
Post by Geoffrey_Coram on Nov 20^th, 2006, 4:30am

qiushidaren wrote on Nov 19^th, 2006, 7:40pm:

i=100*[1.3-v+500*(5-i)]^2

That's an implicit equation, because "i" appears on both sides. I expect you need to solve the quadratic equation so you get an explicit equation, i = function only of v and constants.

Title: Re: Plot I-V Curve by Using Matlab
Post by qiushidaren on Nov 20^th, 2006, 4:40am

Geoffrey_Coram wrote on Nov 20^th, 2006, 4:30am:

qiushidaren wrote on Nov 19^th, 2006, 7:40pm:

i=100*[1.3-v+500*(5-i)]^2

That's an implicit equation, because "i" appears on both sides. I expect you need to solve the quadratic equation so you get an explicit equation, i = function only of v and constants.

Yes, it is an implicit equation, you know sometimes we can't get an explicit equation, or we don't need to solve it to be an explicit one, so I want to know how can I get the correct plot of this kind of implicit equation, thank you in advance!

Title: Re: Plot I-V Curve by Using Matlab
Post by Geoffrey_Coram on Nov 20^th, 2006, 7:42am

Top result from a Google search "matlab implicit plot":

http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=300&objectType=file

Title: Re: Plot I-V Curve by Using Matlab
Post by mg777 on Jan 15^th, 2007, 12:20pm

Besides you're lucky to have a simple quadratic equation. Solve it by hand!

M.G.Rajan
www.eecalc.com